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Asian date mussel (Arcuatula senhousia)

Arcuatula senhousia is a non-native mussel recorded in South Australia, Tasmania, Victoria and Western Australia. It can cluster into dense mats that alter the seabed and affect native species and habitats.

Key facts

Type: Pest animal, invertebrate.

Native to: Western Pacific, from the Russian Far East south to Singapore.

Established in: VIC, TAS, SA, WA.

Other names: Hototogisu, Asian date bag mussel, Musculista senhousia.

Best time to act: Inspect shallow muddy estuaries and bays at low tide, when exposed mussels and mats are easier to find.

Identification

  • This is a small mussel, reaching about 30 mm long, with a smooth, thin shell.
  • The shell is olive green to brown, often with dark radial lines or zigzag markings.
  • Look for fine radiating bands, which may run at right angles to the zigzag pattern.
  • Byssal threads may form a protective cocoon around the shell, and tangled cocoons can create mats on the seabed.
  • Look-alike: Small native mussels can also be olive-brown and patterned, so seek expert confirmation if identification is uncertain.

Where it lives

In Australia it occurs patchily in muddy estuaries and bays, where it burrows into the mud or sits on the surface, sometimes clustering in dense mats.

Why it matters

  • Dense mats can cover and alter seabed habitat and affect organisms living on or in the sediment.
  • The mussels can compete with native species for space and resources.
  • Their byssal cocoons trap sediment and can change the structure of the seabed.

How it spreads

  • Planktonic larvae can disperse with water currents.
  • Mussels or cocoons may be moved between sites on vessels, anchors, marine equipment or transferred shellfish.

Control methods

  • Treat suspected new or localised infestations as a marine pest detection and contact the relevant state or territory biosecurity or marine pest authority before acting.
  • Where removal is authorised, physically collect mussels and their byssal cocoons into a secure container and dispose of them as directed by the authority.
  • Do not use herbicides; use only control methods approved by the relevant authority for the site.
  • Reinspect treated areas and nearby suitable habitat, and report continuing or new detections.

Site hygiene and welfare

  • Before moving between waterways, inspect and clean boats, anchors and marine gear, removing attached mussels, cocoons and sediment.
  • Contain removed material and avoid transferring seawater, mud or shellfish between sites.
  • Use methods set out in the national model codes of practice and standard operating procedures for the species.
  • Coordinate control with neighbours and the local government biosecurity plan, as isolated effort is quickly undone by reinvasion.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Prohibited matter. Report it to Biosecurity Queensland on 13 25 23 within 24 hours and do not move or deal with it. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Prohibited matter. It is an offence to deal with it, and you must notify NSW DPIRD as soon as you become aware of it.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Noxious species. Declared a noxious species under the Fisheries Management Act 2007, so it must not be brought into South Australia, kept, sold or released, and it must not be returned to the water alive. Report any sighting to PIRSA FISHWATCH on 1800 065 522.
  • Western Australia: Noxious fish. Prescribed as a noxious fish under the Fish Resources Management Regulations 1995, so it must not be brought into WA, kept, sold or released. This applies in any area of the State except in the Swan River and Port of Fremantle. Report any sighting to FishWatch on 1800 815 507.
  • Tasmania: Not a declared pest. Not a declared pest or prohibited matter in Tasmania. Importing animals is still controlled by Biosecurity Tasmania.
  • Northern Territory: Not a declared pest. Not on an NT declared or prohibited list. Check with the NT Government before keeping, moving or releasing it.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources